Please read!!!???

when a boy whispers sup in your ear and he stairs at me and says hi very often and sometimes he'll say hi like a billion times more after that and he gets shy around me and sizes me if you dont kno what that means it means that he looks at me from top to bottom or bottom to top.BTW he has a girlfriend and people are saying i should flirt back but like how?tell me examples of to do and say the only times we talk to each other is to ask where my friend bryan is or to say or wave at each other or a smile,during summer vacation the boy i like was in my dreams wich realy creaped me out because i had never met him before and then i came to school and saw him,also one time before we even said hi to eachother in the lunch room he sat infront of me and my friends said he was staring at me alot what do u think of that?he was trying to get my attention by laughing but so was i lol